Reducing Calcium Hardness (CH)?

[cyberalien]

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Several months ago I emptied ~60-70% of the pool and the post-fill CH was 350ppm. I am in Arizona and our water is hard from the tap. So this seems to be about as low as I can go.

Recently tested and am running at about 600ppm. Not sure how the CH increased, as I am only adding muriatic acid and plain bleach for chlorine: my guess is that it is from rocks my landscaper occasionally kicks in or calcium scale removed from walls/etc as it re-balanced.

The calculators say to empty the pool. I really don't want to empty most of it again, just to get to 350ppm.

I've been reading a lot online -- and the advice is always "empty the pool and refill". And every forum post or article I find then mentions something like this: "If the cause is the fill water, commercial hardness reducers or chelating agents will bond with the calcium to keep it trapped in solution."

I try searching for what these products/chemicals are, and basically can't find anything specific. They all allusively seem to mention a set of products that exist, but no mention of a specific product.

Does anyone have any recommendations? (specific links, specific products) Other advice?

Thanks!


Pool is 10,500 gallons, play pool, Phoenix AZ, pebble tec finish. Had it constructed is about ~2 years now.

 

[tim5055]

Welcome to TFP. I don't have your problem, but others here do. Don't panic, high CH can be managed without a refill. Richard or someone else will be along in a moment......

 

[JasonLion]

CH levels up to roughly 1,000 can be managed by lowering the TA and PH to compensate. The higher the CH level, the more care you need to take to make sure that PH doesn't accidentally get out of control at any point.

If you post a complete set of water test results we can give you some more specific advice.

 

[cyberalien]

Test results as of today:

FC 4.5
CC 0
PH 8+
TA 100
CH 600
CYA 40

I added 2 cups of acid, which should bring PH down to acceptable range.

I had a horrible problem this last summer of CYA being 100+ --- how I learned about this forum and switching to chlorine instead of the trichlor pucks. Finally happy to have it down to 40. Now just trying to solve the CH part.

Let's assume I stop worrying about CH and just keep TA/PH in check. I can see from the site's calculator that keeping TA around 100 and PH around 7.5 puts CSI at 0.3 (good). But if I add acid, PH goes down, TA goes down... the PH will then rise as water aerates (water feature). Seems like a constant back-n-forth to those in check.

For more context, testing I did last summer on my fill water:
FC 1.0
CC 0.0
PH 7.8
TA 120

 

[JasonLion]

Right now, if you keep PH below 7.8 you should be fine. As CH goes up, you will also need to keep TA lower.

You do get into a kind of back and forth situation. The water feature will raise the PH back up, and you will need to add more acid. Over time TA will come down, but as soon as you top off the pool with some fresh water the TA will go back up, so more acid, and so on. As the CH level goes up you end up adding acid more and more frequently.

 

[cyberalien]

Back to original question... are there specific chelating/sequestrant agents or products I could add to pool to offset the calcium?

Might be more economical to use such a product to get CH closer to 300 again, then balance out with PH/TA.

Online reading reminds me that calcium is actually a metal, and a lot of the metal removers (typically used for iron, copper, etc) would also remove calcium, though the chemical property is usually to get iron/copper/etc first. given my pool probably has zero/little of these chemicals --- seems one of these or one geared specifically to calcium would probably help.

 

[JasonLion]

You can use a sequestrant (any will do something but one tuned for calcium will work best) to help prevent calcium scaling. However, it gets expensive. Sequestrant does not remove the calcium from the water, it only prevents scaling. Meanwhile, sequestrant breaks down slowly so more needs to be added regularly. As CH goes up, you need to use more and more sequestrant, which quickly becomes impractically expensive.

In the Phoenix area you can get a reverse osmosis treatment, which will lower the CH level, but again it can be a bit on the expensive side.

 

[chiefwej]

If you have allowed the pH to run high in the past, the extra CH that you found after draining and refilling no doubt, came from scale that was on the pool surfaces. You are getting the idea that the most important number isn't CH but CSI. Let it get too high and you have scale, too low and it will damage the pool.

I have successfully managed an entire season with my CH above 1,000. It isn't easy and requires constant monitoring, testing and careful balancing. Kind of like walking a tight rope. As the CH gets higher it becomes more important to regularly test and rebalance, keeping a careful eye on the resulting CSI. I find that my fill water tests CH around 350-400. But any time I drain and refill the pool water will shortly be testing about 500 or so. It's just part of the joy of living in AZ.

 

[Richard320]

Maintaining decent chemistry and avoiding scale is not a big deal until CH gets above 800, and then it gets very difficult. As the Chief says, it's a tightrope. You have a limited range of pH adjustment before you start corroding plumbing and burning eyes, you can't do much about the temperature or the Calcium. That leaves TA. And you don't have a whole lot of wiggle room there, either. The long-term solutions are water replacement or reverse osmosis. R/O is available in your area. The company is called Calsaway. It's probably cheaper to replace water. But test your fill water before you decide. If it's coming out the tap at 400 CH, replacing half the water would only get the pool down to 500.